Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

Replacing new hybrid

I live in the Pacific Northwest and have a 5 year-old hybrid, propane heating system that heats water to 165 deg and runs through a coil in an air handling unit to provide forced air heating. There are two air handlers (2 ton and 3 ton) with 3 zones on each one for a two story, 4300 sq ft. house with 10 ft and 9 ft ceilings. The heat / water source is a 100 gallon tank (A.B. White) that is heated with 199,000 BTU's. The system also provides domestic hot water by dumping cold water in the line to bring the temp down to an acceptable 120 deg. The problem is my monthly propane bills are typically around $1,000 per month in the winter and $800 to $900 in the summer to heat the water. (I set the tank temp down to 120 in the summer.)

My wife and I will retire within four years and, although we are not happy to replace relatively new HVAC equipment, we don't want to pay this exorbitant monthly cost to heat our house and water on a fixed income. We intend to replace the system before winter sets in. Average winter temps here are in the 40's with occasional dips into the low 30's and high 20's. Summer temps are typically in the 80's and 90's with occasional spikes to 100 & 104 degrees. I have 2 ton and 3 ton A/C units for summer cooling that struggle in the higher temps.

I received bids from three HVAC contractors to replace the system with 2 heat pumps and an alternative heat source as a backup. Two contractors (reps for Trane and Coleman) bid to install propane forced air units as the backup source. The third contractor (a Carrier rep) recommends a heat strip to replace the water coils in the existing air handlers. What are the pros and cons of each heat source system?

I also intend to replace the hot water tank with 2 tankless units -- Rinnai 94LSI or Navien 240A. The Navien stats are the most impressive but the company web site represents the parent company as a 33 year-old boiler maker in Seoul, South Korea that has been licensed in the US since 2003 trying to establish a market share here. It does not have a track record in the US to determine if there are service issues to compare with Rinnai. My e-mail to Navien/US asking about service issues has gone unanswered. Does anyone have experience with the Navien product?

The cost for LP is $2.75 per gallon and electric is 10 cents/KWH. I have other appliances (cooktop, BBQ, and fireplace log lighter) that require propane so I will not be getting rid of the tanks and will continue to lease them. (There are two 125 gal tanks because of code restrictions for their location.)

The Carrier contractor provided an annual Operating Cost Estimate sheet that compares a propane FAU with other Carrier electric units. His estimate is based on gas at $3.08/gal. with 64,672 BTUh for heating costs and 41,588 BTUh cooling capacity. Adjusting for the lower LP cost, the estimated annual operating cost differential with the electric option for an Infinity 16 is almost $4,000 less per year than an LP unit. The installation cost of the electric system is also several thousand dollars less than propane.

The decision of which system to purchase seems to be a no-brainer but when the information seems to be this good/significant I become suspicious and look for the "yes, but" clause -- like listening for what a politician or used car salesman is not saying. This is why ask for your comments about the pros and cons of each system.